Table of Contents


Version 2.5.1



  • New functions for conversion between mpd_t and a decimal triple with a split uint128_t coefficient.

  • All symbols in the header files now have an MPD_* or mpd_* prefix.

  • libmpdec/.objs/symbols64.exp and libmpdec/.objs/symbols32.exp contain all symbols of the exported API. The files are almost identical, but mpd_qsset_i64, mpd_sset_i64, mpd_qsset_u64 and mpd_sset_u64 are only available in the 64-bit build.

    libmpdec/.objs/libmpdec.imp is the unified 64/32-bit import file for AIX.

  • The new test target make check_local does not attempt to download This is useful for packagers whose infrastructure does not allow downloading during the testing phase.

    make check is still preferable because it runs all tests.

style fixes

  • Apply several clang-tidy suggestions (high diagnostic level).

build features

  • AIX: full support for xlc/gcc builds in ./configure.
  • full support for AIX-style shared libraries.
  • full support for AIX multilib header.

build fixes

  • Update config.guess and config.sub in order to support IBM Power architectures.
  • Fix false positive _FORTIFY_SOURCE warning on Fedora.



  • New methods for conversion between Decimal and a decimal triple with a split uint128_t coefficient.

  • decimal::Context now uses default constructors wherever possible.

  • AIX: The tests now have a –pthread option. The default thread stack size on AIX (96K) makes std::thread unusable for, which needs around 300K.

  • Windows: The DLL can now be built. Since DLLs do not support the C++11 extern thread_local context, each translation unit gets its own static reference to the thread_local context. This should preserve the semantics at the expense of clarity.

    Note that this scheme is specific to the DLL build; the static library build on Windows as well as all other operating systems (except for OpenBSD and Solaris) use the C++11 extern thread_local context.

  • OpenBSD, Solaris: The shared library now works using the above scheme. For simplicity, both the shared and static libraries use the workaround.

style fixes

  • Apply several clang-tidy suggestions (high diagnostic level).

bug fixes

  • DecimalException now inherits from std::runtime_error instead of std::exception. This automatically provides a nothrow copy constructor.
  • Use mpd_free() instead of free(). This only affects applications using the libmpdec custom allocators.

build fixes

  • Undefine some additional math.h macros for non-compliant C++11 implementations.
  • libmpdec++ is now linked against libmpdec.

Version 2.5.0

New: libmpdec++

libmpdec++ is a new C++ library around libmpdec. It frees users from manual memory management and allows cleaner code using inline operators.

libmpdec++ has a thread local context, so inline operators work seamlessly with threaded code.


  1. New functions mpd_qset_string_exact, mpd_qset_i64_exact and mpd_qset_u64_exact.

  2. For very large precisions like MPD_MAX_PREC libmpdec failed with MPD_Malloc_error even when the result was exact and required far fewer digits.

    Now libmpdec retries the operation with the smallest possible precision for exact results.

  3. ./configure now has the –enable-profile option for easier profile guided optimization builds. Using PGO, recent compilers produce better optimized libraries with speedups in the order of 20%.

  4. C++ use: All headers now assume at least C++11, so a couple of hacks have been removed from the headers. C++ compatibility is fully tested in libmpdec++.

behavior changes

  1. The functions mpd_ceil, mpd_floor and mpd_trunc now set MPD_Invalid_operation when the input is NaN or Infinity.

    Previously they returned special values unchanged. That behavior was inspired by the similar to_integral function from the specification, but does not seem useful for the above functions.

build fixes

  1. OS X: Linking has been completely reworked and now uses .dylib.
  2. Windows: vcstdint.h has been removed, Windows now supports stdint.h.

bug fixes

  1. A couple of quiet functions have been made resilient against being called with a “dirty” status. Note that it is not recommended in general to call quiet functions with any status other than 0.

  2. In runtest.c, fma_eq.decTest and powmod_eq.decTest operands were accidentally reversed for the op_eq_eq tests.

    Since both the code and the tests assumed reversed operands, the tests were correct. However, for readability this situation has been fixed.

Version 2.4.2

build fixes

  1. ICC/Windows: the optimized x86 build requires -fp-model=precise.
  2. OS X: the linker requires -dynamiclib and -install_name for building a shared library.

Version 2.4.1

build fixes

  1. The __uint128_t detection in ./configure has been fixed . Failure to detect the option resulted in building the significantly slower ANSI target on non-x86/amd64 platforms.
  2. Use -fPIC instead of -fpic to fix a build failure on SPARC platforms.
  3. Split the tests into a faster “make check” and a slower “make check_alloc”. The latter tests allocation failures but is too slow on older machines.
  4. Generate detailed test output for better feedback on slower machines.
  5. The static library is now built without -fPIC, which is significantly faster at least on x86. Both the static and the shared library are now tested separately.

bug fixes

  1. PEP 3101 formatting: With the ‘%’ format type, a trailing percent sign is now also added for infinities and NaNs.

Version 2.4.0


  1. Faster integer to string conversion.
  2. mpd_qln(), mpd_qlog10() and mpd_pow() are now thread-safe.
  3. All functions that take or return C integers are now available in both the 64-bit and the 32-bit builds.
  4. Support for cross-compiling.
  5. Scripts for Visual Studio builds.

code improvements

  1. This version is exactly the same as the version shipped with Python-3.3+. Large portions of the code have been refactored in order to facilitate proofs. Many ACL2 proofs have been added.


  1. The Python module has been removed from mpdecimal, since both libmpdec and cdecimal are included in Python-3.3+.
  2. The large test suite against decNumber as well as the multi-precision tests against gmp have been removed, but will be available in a separate package. Naturally these tests are still run as part of the release process.

Version 2.3


  1. New test suite with comprehensive tests against decNumber.
  2. Full support for compilers without uint64_t (tested with CompCert).

bug fixes

  1. If ROUND_FLOOR is set and the operand is zero, the functions mpd_plus() and mpd_minus() have special cases for the sign of the result.

Version 2.2

build process

  1. configure: append CFLAGS to CONFIG flags.
  2. Makefile: use includedir, libdir, datarootdir, datadir, docdir, DESTDIR.

workarounds for toolchain bugs

  1. Enable workaround for a gcc miscompilation. See:

  2. Enable workaround for the glibc _FORTIFY_SOURCE/memmove bug, which is exposed by gcc-4.6. See:


  1. Make PPRO inline assembly PIC-compliant (for the dynamic library).

Version 2.1

Version 2.1 was never released, but escaped into the wild via the Makefile and in cdecimal-1.97-rc2.tar.gz. Both files already had that version number.


  1. Code coverage increased to 100%. This includes every possible allocation failure.
  2. Switch build process to ./configure.
  3. Makefile targets for creating coverage reports.

bug fixes

  1. mpd_qget_uint, mpd_qget_u64, mpd_qget_u32 did not raise for negative input.
  2. Handle allocation failures in _mpd_fntmul under extreme conditions.

Version 1.2.1

bug fixes

  1. With MACHINE=ansi64, the macros BSR and BSF used x86 assembly. This caused compilation to fail on non-x64 platforms.

Version 1.2


  1. Support for compilers with __uint128_t (option MACHINE=ansi64).
  2. Support for other 64-bit compilers (option MACHINE=ansi64c32).
  3. Support for legacy compilers without uint64_t (option MACHINE=ansi-legacy).
  4. Slightly different build process (please read INSTALL.txt).
  5. If clamp=1, the maximum payload length of a NaN is prec-1.

bug fixes

  1. Fix for mpd_qround_to_int, which did not handle digits exceeding the context precision correctly in all cases.
  2. In rare corner cases Underflow was not set in transcendental functions.